Second-trimester fetal growth and the risk of poor obstetric and neonatal outcomes.

OBJECTIVE: To compare outcomes of fetuses with an estimated fetal weight (EFW) < 25(th) percentile in the second trimester to those in fetuses with EFW >or= 25(th) percentile in the second trimester.
METHODS: We compared outcomes of 252 pregnancies with an EFW < 25(th) percentile at 18-24 weeks' gestation with those of 265 controls. All pregnancies had early dating by ultrasonography. We excluded fetuses with aneuploidy, major malformations, second-trimester rupture of membranes, and multiple pregnancies.
RESULTS: Second-trimester EFW < 25(th) percentile was significantly associated with higher rates of fetal or neonatal death, third-trimester small for gestational age (SGA), Doppler abnormalities, indicated preterm birth, gestational hypertension or pre-eclampsia before labor, lower birth weight, birth weight < 10(th) percentile, birth weight < 5(th) percentile, and admission to the neonatal intensive care unit. Many of these associations remained even after excluding patients with oligohydramnios, fetal echogenic bowel, and growth asymmetry.
CONCLUSION: Second-trimester SGA, as defined by an EFW < 25(th) percentile using current growth curves, is associated with poor obstetric and neonatal outcomes. Increased surveillance of such pregnancies may be necessary.